1. Field of the Invention
The present invention relates generally to lipid microtubules and more specifically to lipid microtubules having a high aspect ratio.
2. Description of the Background Art
The production of lipid microstructures has previously been described in U.S. Pat. Nos. 4,877,501, 4,911,291 and 4,990,291, and U.S. Ser. No. 08/703,608, filed Aug. 27, 1996 by Price et al, the entireties of all of which are incorporated herein by reference for all purposes. The methods use an alcohol and water phase for the production of lipid microcylinders by direct crystallization. None of these patents teach an optimum method for producing very high aspect ratio lipid microcylinders (typically above about an average aspect ratio of about 20, and commonly having an average aspect ratio of about 50 or more), at high yield rates (e.g., at about 50 or higher) and then preserving that high aspect ratio during subsequent processing steps.
Currently, the alcohol and water mixed solvent bath that may be varied over a very wide range of concentrations to produce lipid microcylinders from a polymerizable lecithin. These methods address the use of a single alcohol and do not predict the activity of mixed solvents, the effect of mixed solvents on the morphology of the resulting microcylinders, or the effect of mixed solvents on the process yield.
In current methods control of the number of lipid bilayers is achieved by varying the alcohol/water concentration as well as the lipid concentration. This control of the number of lipid bilayers is described in U.S. Ser. No. 08/703,608, the entirety of which is incorporated herein by reference. However, no method exists for production of microcylinders at very high aspect ratios while at the same time preserving bilayer numbers between 2 and 4. At low concentrations the bilayer walls are single bilayers and as concentration increases the number of bilayers increases.
Previously described methodologies that produce high aspect ratio lipid microstructures have resulted in single walled microcylinders at such high numbers that the solutions are highly thixotropic, thus frustrating attempts at further processing without so much shearing of the resultant tubules that they become useless for further metallic plating.
Also, previous methods of electroplating lipid tubules often degraded the aspect ratios and/or cause the lipid tubules to "clump" or "weld".